A secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, a middle or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight and the manufacturing cost of the pouch-shaped battery is low.
Meanwhile, for the battery module to provide output and capacity required by a predetermined apparatus or device, it is necessary for the battery module to be configured to have a structure in which a plurality of battery cells are electrically connected to each other in series or in parallel. In addition, it is necessary for the battery module to be configured to have a structure which is easily extendable and stable as the capacity of the battery module is increased. Particularly, in a case in which a plurality of battery cells is used to constitute the battery module or a plurality of cell modules, each of which includes a predetermined number of battery cells, is used to constitute the battery module, a plurality of members, such as bus bars, for mechanical fastening and electrical connection between the battery cells or the cell modules is generally needed and, as a result, a process of assembling such members is very complicated.
For example, conventionally, a power cable or bus bars are used to directly achieve electrical connection of the battery module. In this case, however, a short circuit due to a tool may occur during electrical connection of the battery module. On the other hand, the battery module may be misassembled.
Particularly, for the power cable, great force is needed depending upon the specification of electric current supplied to the power cable. In order to solve this problem, methods of easily achieving electrical connection using an additional connector or a plug-in connector have been proposed. Even in these methods, however, additional members are needed with the result that the number of unnecessary parts is increased.
There is needed a space for coupling, welding, or soldering the mechanical fastening and electrical connection members with the result that the total size of a battery system is increased. The increase in size of the battery system is not preferable in an aspect of the spatial limit of an apparatus or device in which the battery module is mounted.
Therefore, there is a high necessity for a middle or large-sized battery pack that can be easily assembled with fundamentally secured safety while solving the above problems.